/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.io.xml;



import com.bff.gaia.unified.sdk.coders.CoderException;

import com.bff.gaia.unified.sdk.coders.CustomCoder;

import com.bff.gaia.unified.sdk.util.EmptyOnDeserializationThreadLocal;

import com.bff.gaia.unified.sdk.util.VarInt;

import com.bff.gaia.unified.sdk.values.TypeDescriptor;

import com.bff.gaia.unified.vendor.guava.com.google.common.io.ByteStreams;



import javax.xml.bind.JAXBContext;

import javax.xml.bind.JAXBException;

import javax.xml.bind.Marshaller;

import javax.xml.bind.Unmarshaller;

import java.io.*;

import java.util.Objects;



/**

 * A coder for JAXB annotated objects. This coder uses JAXB marshalling/unmarshalling mechanisms to

 * encode/decode the objects. Users must provide the {@code Class} of the JAXB annotated object.

 *

 * @param <T> type of JAXB annotated objects that will be serialized.

 */

public class JAXBCoder<T> extends CustomCoder<T> {



  private final Class<T> jaxbClass;

  private transient volatile JAXBContext jaxbContext;

  private final EmptyOnDeserializationThreadLocal<Marshaller> jaxbMarshaller;

  private final EmptyOnDeserializationThreadLocal<Unmarshaller> jaxbUnmarshaller;



  public Class<T> getJAXBClass() {

    return jaxbClass;

  }



  private JAXBCoder(Class<T> jaxbClass) {

    this.jaxbClass = jaxbClass;

    this.jaxbMarshaller =

        new EmptyOnDeserializationThreadLocal<Marshaller>() {

          @Override

          protected Marshaller initialValue() {

            try {

              JAXBContext jaxbContext = getContext();

              return jaxbContext.createMarshaller();

            } catch (JAXBException e) {

              throw new RuntimeException("Error when creating marshaller from JAXB Context.", e);

            }

          }

        };

    this.jaxbUnmarshaller =

        new EmptyOnDeserializationThreadLocal<Unmarshaller>() {

          @Override

          protected Unmarshaller initialValue() {

            try {

              JAXBContext jaxbContext = getContext();

              return jaxbContext.createUnmarshaller();

            } catch (Exception e) {

              throw new RuntimeException("Error when creating unmarshaller from JAXB Context.", e);

            }

          }

        };

  }



  /**

   * Create a coder for a given type of JAXB annotated objects.

   *

   * @param jaxbClass the {@code Class} of the JAXB annotated objects.

   */

  public static <T> JAXBCoder<T> of(Class<T> jaxbClass) {

    return new JAXBCoder<>(jaxbClass);

  }



  @Override

  public void encode(T value, OutputStream outStream) throws IOException {

    encode(value, outStream, Context.NESTED);

  }



  @Override

  public void encode(T value, OutputStream outStream, Context context) throws IOException {

    if (context.isWholeStream) {

      try {

        jaxbMarshaller.get().marshal(value, new CloseIgnoringOutputStream(outStream));

      } catch (JAXBException e) {

        throw new CoderException(e);

      }

    } else {

      ByteArrayOutputStream baos = new ByteArrayOutputStream();

      try {

        jaxbMarshaller.get().marshal(value, baos);

      } catch (JAXBException e) {

        throw new CoderException(e);

      }

      VarInt.encode(baos.size(), outStream);

      baos.writeTo(outStream);

    }

  }



  @Override

  public T decode(InputStream inStream) throws IOException {

    return decode(inStream, Context.NESTED);

  }



  @Override

  public T decode(InputStream inStream, Context context) throws IOException {

    try {

      if (!context.isWholeStream) {

        long limit = VarInt.decodeLong(inStream);

        inStream = ByteStreams.limit(inStream, limit);

      }

      @SuppressWarnings("unchecked")

      T obj = (T) jaxbUnmarshaller.get().unmarshal(new CloseIgnoringInputStream(inStream));

      return obj;

    } catch (JAXBException e) {

      throw new CoderException(e);

    }

  }



  private JAXBContext getContext() throws JAXBException {

    if (jaxbContext == null) {

      synchronized (this) {

        if (jaxbContext == null) {

          jaxbContext = JAXBContext.newInstance(jaxbClass);

        }

      }

    }

    return jaxbContext;

  }



  @Override

  public TypeDescriptor<T> getEncodedTypeDescriptor() {

    return TypeDescriptor.of(jaxbClass);

  }



  @Override

  public boolean equals(Object other) {

    if (other == this) {

      return true;

    }

    if (!(other instanceof JAXBCoder)) {

      return false;

    }

    JAXBCoder<?> that = (JAXBCoder<?>) other;

    return Objects.equals(this.jaxbClass, that.jaxbClass);

  }



  @Override

  public int hashCode() {

    return jaxbClass.hashCode();

  }



  private static class CloseIgnoringInputStream extends FilterInputStream {



    CloseIgnoringInputStream(InputStream in) {

      super(in);

    }



    @Override

    public void close() {

      // Do nothing. JAXB closes the underlying stream so we must filter out those calls.

    }

  }



  private static class CloseIgnoringOutputStream extends FilterOutputStream {



    CloseIgnoringOutputStream(OutputStream out) {

      super(out);

    }



    @Override

    public void close() {

      // JAXB closes the underlying stream so we must filter out those calls.

    }

  }

}